Coating material tests

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lycium
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Re: Coating material tests

Post by lycium » Fri Dec 07, 2012 5:15 am

Perhaps relevant is chapter 3 of these course notes: http://mesh.brown.edu/3DPGP-2007/pdfs/sg06-course01.pdf

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Re: Coating material tests

Post by OnoSendai » Fri Dec 07, 2012 5:55 am

I'm tempted to see what you guys (CTZn and Galinette) can achieve with a curvature function in ISL, so I'll try adding it in soon :)

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CTZn
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Re: Coating material tests

Post by CTZn » Fri Dec 07, 2012 8:23 am

OnoSendai wrote:I'm tempted to see what you guys (CTZn and Galinette) can achieve with a curvature function in ISL, so I'll try adding it in soon :)
May your hand not tremble in doing so.

The last time I've been thinking at that feature was while doing the liquid coating. Accessing curvature data can be considered as an ancient request :)
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Re: Coating material tests

Post by CTZn » Fri Dec 07, 2012 8:37 am

galinette wrote:
CTZn wrote:Thanks Tom !

The next one can get real creepy sometimes... noise fun.
Some physicist comment:
It's too visible that you only use the normal for computing the thickness. This leads to some undesirable effects:
- The sharp angles show a sharp change in thickness
- The top flat part of the base has virtually nothing on it, while it should be one of the thickest (it's at the bottom, plus it's lying flat so the liquid should not flow from it

Some more advanced shader could make use of the altitude as well as the normal. [...]
Sorry for criticizing, that's looking very good (and scary :? )

Cheers,

Etienne
It's clealy an artistical approximation, vehiculating the idea that some fluid that was around ended below eventually.

I did not even test the material on a different mesh, it was really made against a sphere and is expected to work best on closed, smooth shapes. The use of 2*Pi in the power illustrates that over-adaptation of the shader to the one mesh. Again, I just eyeballed that 2*Pi couldn't be wrong against a spherical thing, period :lol:

Now, it belongs to me to discriminate between what is a positive criticism and what's not. I'm litterally hungry for the former. You'll never profess the other kind without me telling you, and irritably enough I can defend myself :twisted:

Everyone here should know that my authority is all symbolical (it's a badge) and that I'm sad that many don't dare to criticize up to my doings. Mark my words and thank you again !
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CTZn
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Re: Coating material tests

Post by CTZn » Fri Dec 07, 2012 9:37 am

CTZn wrote:The use of 2*Pi in the power illustrates that over-adaptation of the shader to the one mesh. Again, I just eyeballed that 2*Pi couldn't be wrong against a spherical thing, period :lol:
See how I can say stupid things at time ? No one cares :cry: 8)

There's in fact no relationship between the shape of the mesh and the way Pi is used in that shader. That non-sense illustrates my abscence of background in physics.
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Re: Coating material tests

Post by OnoSendai » Fri Dec 07, 2012 11:16 am

Gaussian curvature:
Red = positive curvature, green = negative curvature.
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curvature_shader_test.jpg

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Re: Coating material tests

Post by OnoSendai » Fri Dec 07, 2012 11:36 am

A test with the coating thickness based on Gaussian curvature.

It kind of works in this case, however I don't think Gaussian curvature is the right curvature metric to use for this kind of thing, because a crease in a flat surface will have zero Gaussian curvature.
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curvature_based_coating_thickness.jpg
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galinette
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Re: Coating material tests

Post by galinette » Fri Dec 07, 2012 12:30 pm

OnoSendai wrote:A test with the coating thickness based on Gaussian curvature.

It kind of works in this case, however I don't think Gaussian curvature is the right curvature metric to use for this kind of thing, because a crease in a flat surface will have zero Gaussian curvature.
Yes, we need the sum of curvatures and not the product
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Re: Coating material tests

Post by StompinTom » Sat Dec 08, 2012 1:28 am

Woo. Easy dirt shader?

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lycium
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Re: Coating material tests

Post by lycium » Sat Dec 08, 2012 1:37 am

Yes I was thinking this too! Add some FBm / noise, and suddenly you have your worn crevices shader!

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CTZn
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Re: Coating material tests

Post by CTZn » Sat Dec 08, 2012 2:50 am

Worn edges is indeed the primary shading application of curvature evaluation !
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galinette
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Re: Coating material tests

Post by galinette » Sat Dec 08, 2012 3:02 am

Hey, why did nobody request for this before I did :)
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Re: Coating material tests

Post by Zom-B » Sat Dec 08, 2012 3:04 am

galinette wrote:Hey, why did nobody request for this before I did :)
Our requests are less to the point, but more of "make that magic happen" kind of stuff ;)
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Re: Coating material tests

Post by OnoSendai » Sat Dec 08, 2012 3:11 am

There has been a somewhat similar request for an ambient occlusion pass/info, which is a lot more complicated.

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Re: Coating material tests

Post by FoXar » Sat Dec 08, 2012 12:02 pm

OnoSendai wrote:There has been a somewhat similar request for an ambient occlusion pass/info, which is a lot more complicated.
Nice materials! Can't wait to try and make a fruit pie with a nice jelly coating on top of it :D

About that ambient occlusion, I'm still holding you on that one! Would finally make those mouldings and finer details pop a bit more. :wink:
Cheers,
Roo Evans

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